Dull bit indicator



Arm/ W5? J R YANCEY DULL BIT INDICATOR Filed. Feb. 10, 1949 April 17, 1951 Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE DULL BIT INDICATOR John R. Yancey, Houston, Tex.

Application February 10, 1949, Serial No. 75,708

2 Claims.

This invention relates to a dull bit indicator.

A general object of the invention is to provide means whereby the pressure of the drilling fluid will indicate to the operator that the drill has worn oil, or become dull, to an extent to render it inefficient.

The drill is of the blade type and is equipped with means which will allow an increase in the volume of drilling fluid flowing through the drill and a consequent decrease in the pressure of the drilling fluid thus effecting the operation of the pump which in turn will give the desired indication.

It is a further, and more specific, object of the invention to provide, in a drill, a relief port which is normally closed by means of a plug with a metal bar, welded at both ends to the drill, for maintaining the plug in closed position, said bar being composed of a metal that will readily bend so that the bar may be bent outwardly and thus rendered inoperative when the drill becomes dull and the lower weld is worn away to allow the plug to be displaced by the pressure of the drilling fluid to the end that said pressure will be suddenly lowered.

Other objects and advantages will be apparent from the following specification which is illustrated by the accompanying drawings, wherein:

Figure l is an edge view of a drag type drill, shown partly in section.

Figure 2 is an elevation'al view thereof, and

Figure 3 is an edge view of the drill in dulled state with the plug displaced.

Referring now more particularly to the drawings the numeral 1 designates a drill head which is formed of steel, or other suitable metal, and is provided with depending oppositely disposed blades 2, 2.

The drill is shown attached to the lower end of a conventional drill stem 3 whose lower end is screwed into the head I and leading from the stem through the body of the drill there are the drilling fluid discharge passageways 4, 4 which terminate in front of the respective blades 2.

As is indicated in Figures 1 and 3 there is a lateral bore 5 leading outwardly from one of the passageways 4 and in this bore 5 there is a tubular liner 6 of suitable hard material and whose outer end is enlarged providing an inside annular outwardly facing shoulder I.

A plug 8 is fitted into the liner 6 and has a resilient seal ring 9 around the plug and preferably this plug is provided with an annular rim l0 which rests against the shoulder 1.

During drilling operations the plug is maintained in place by means of a bar II which extends diagonally of the corresponding blade across the plug and whose ends are welded to the drill by the welds l2, [3.

During ordinary drilling operations, therefore the liner 6 will be closed by the plug and the drilling fluid will be forced down through the passageways 4, 4 ahead of the forward faces of the blades to carry away the cuttings.

Of course the lower ends of the blades or cutters will gradually wear away and eventually the lower weld l3 will be destroyed so that the lower end of the bar II will be free and the high pressure Within the drill will force the plug 8 outwardly thus moving the lower free end of the bar outwardly so as to permit displacement of the plug 8 by the pressure within the drill as is indicated in Figure 3.

Thereupon the pressure of drilling fluid will drop suddenly and the pump will speed up thus indicating to the driller that the drill has become sufficiently worn away to be of no further service in the bore and the drill stem may then be withdrawn and a new drill substituted for the one that has worn out.

In order to protect the bar ll during drilling operations there are the guards l4, M on opposite sides of the bar II and these guards alsoare curved around the opposite side of the bore 5 as indicated in Figure 2. These guards may be secured to the drill in any approved manner as by welding.

The drawings and description disclose what is now considered to be a preferred form of the invention by way of illustration while the broad principle of the invention will be defined by the appended claims.

What I claim is:

1. A drill bit having cutting blades at its lower end and having a passageway therethrough for the flow of flushing fluid from the drill stem into the well, said bit having a relief port in communication with said passageway, a displaceable plu fitted into said relief port, a retaining bar positioned over said relief port and welded at its end on the outer side of the bit to maintain said plug in said port, one of said ends being welded to the bit beneath said plug and guards on the bit on opposite sides of the bar and approximately co-extensive, in length, with said bar.

2. A drill bit of the blade type having a passageway therethrough for the flow of flushing fluid from the drill stem into the well, said bit being secured to said stem and said bit having a relief port in communication with said passageway, a displaceable closure for said port, a bar across said closure on the outer side of the bit whose ends are welded to the bit, one of said ends being welded to the bit below the relief port and positioned to be released by wear of the bit, said bar, when so released, being displaceable under the influence of the pressure of the fluid to permit displacement of the closure and guards secured to the bit on opposite sides of, and adjacent, the bar and relief port.

JOHN R. YANCEY.

No references cited. 

